Homie, Au-197 is what's being created, as stated in the screenshot, and it is the stable isotope of gold. It's the naturally occurring one.

And the reaction doesn't need to be especially stable on its own when it is a bonus byproduct of existing fusion reactor processes. The point is that we can take existing and new reactors, add this process, and immediately gain significantly extra value from the stuff we're already doing.

it's like hybrid electric cars that charge their batteries using the brakes. You're already braking and losing a ton of energy as waste. ANY way to recapture and use that waste energy that yields more value than the materials required to capture it, is an immediate win.